It has been shown that membrane lipid changes alter the receptor properties of certain membranes, that lipid changes can occur very rapidly and that drugs, such as ethanol, can alter the fluid properties of certain membranes. These data suggest that certain drug dependencies may be related to membrane alterations as a cause and effect. We propose to first determine how long it takes rats to become dependent on the drug ethanol. Once dependent, we propose to study brain synaptosomes and/or synaptic membranes to determine: 1. if the membrane fatty acids have been altered, 2. if the phospholipids have been altered, 3. if the intrinsic fluidity has changed, 4. if certain enzymes which metabolize fatty acids and phospholipids have been altered, and 5. if the above alterations can be related to possible changes in a membrane enzyme (Na+ + K+ ATPase) known to be affected by membrane lipid changes. By correlating the above data we hope to propose a mechanism of drug induced dependence. If such a mechanism involving fluidity is postulated, then additional studies would be proposed in a subsequent grant application which would attempt to determine if the fluidity theory applied to a variety of other drugs.